Market size is the total revenue potential of a market, typically expressed via the TAM/SAM/SOM framework. It's used to communicate the scale of the opportunity to investors, board, and team, and to inform strategic decisions about market entry and expansion. The discipline is to estimate market size bottoms-up (specific customer counts × prices) rather than tops-down (small percentage of huge market), because tops-down estimates are universally distrusted by sophisticated investors. It is one of the most-scrutinized elements of fundraising pitches.
The standard framework:
TAM (Total Addressable Market):